1. Field of the Invention
This invention relates to a novel reaction product additive composition for use in motor fuels. The additive comprises the imide reaction product obtained by reacting a hydrocarbyl-substituted dibasic acid anhydride with a random backbone polyoxyalkylene diamine to produce a motor fuel-soluble bisimide which provides a number of valuable properties in a motor fuel composition.
The combustion of a hydrocarbon motor fuel in an internal combustion engine leads to the formation and accumulation of deposits on various parts of the combustion chamber as well as on the fuel intake and exhaust system of the engine. The presence of deposits in the combustion chamber seriously reduces the operating efficiency of the engine. First, deposit accumulation within the combustion chamber inhibits heat transfer between the chamber and the engine cooling system. This leads to higher temperatures within the combustion chamber, resulting in increases in the end gas temperature of the incoming charge. Consequently, end gas auto-ignition occurs, which causes engine knock. In addition, the accumulation of deposits within the combustion chamber reduces the volume of the combustion zone, causing a higher than design compression ratio in the engine. This, in turn, can also lead to engine knocking. A knocking engine does not effectively utilize the energy of combustion. Moreover, a prolonged period of engine knocking can cause stress fatigue and wear in pistons, connecting rods, bearings and cam rods of the engine. The phenomenon noted is characteristic of gasoline powered internal combustion engines. It may be overcome by employing a higher octane gasoline which resists knocking for powering the engine. This need for a higher octane gasoline as mileage accumulates has become known as the engine octane requirement increase (ORI) phenomenon. It is particularly advantageous if engine ORI can be substantially reduced or eliminated by preventing or modifying deposit formation in the combustion chambers of the engine.
Another problem common to internal combustion engines relates to the accumulation of deposits in the carburetor. These deposits tend to restrict the flow of air through the carburetor at idle and at low speed resulting in an over-rich fuel mixture. This condition also promotes incomplete fuel combustion and may lead to rough engine idling and even engine stalling. This condition leads to the production of excessive hydrocarbon and carbon monoxide exhaust emissions. It would therefore be desirable from the standpoint of engine operability and overall air quality to provide a motor fuel composition which minimizes or overcomes the above-described problems.
A third problem common to internal combustion engines is the formation of intake valve deposits. Intake valve deposits interfere with valve closing and eventually result in valve burning. Such deposits interfere with valve motion and valve seating and tend to reduce the volumetric efficiency of the engine and to limit maximum power. Valve deposits may be produced from thermally and oxidatively unstable fuel or from lubricating oil oxidation products. The hard carbonaceous deposits produced collect in the tubes and runners that are part of the exhaust gas recirculation (EGR) flow. These deposits are believed to be formed from exhaust particles which are subjected to rapid cooling while mixing with the air-fuel mixture. Reduced EGR flow can result in engine knock and in nitric oxide, NO.sub.x, emission increases. It would therefore be desirable to provide a motor fuel composition which minimizes or overcomes the formation of intake valve deposits.
An essential property of a motor fuel additive relates to its sensitivity to water. Motor fuels, in general, may Interface with or be mixed with water in the fuel distribution system. This problem commonly occurs in tank farm storage tanks as well as in underground service station storage tanks. To a limited extent, water may be present in vehicle fuel tanks. Additives that are highly sensitive to water tend to form an insoluble dispersion in the fuel, producing a hazy or cloudy fuel. In the presence of the fuel and water, the additive may also form a significant amount of a distinct thick emulsion layer in the fuel bottoms. The formation of a dispersion and of an emulsion layer in the fuel represents a loss of the normally soluble additive from its intended use in the fuel and may substantially diminish the properties of the fuel product. The formation of a distinct emulsion is more significant since it may interfere with the proper operation of engine fuel injectors because of the fine tolerances of their metering systems. It is highly desirable to provide an additive that is resistant to the formation of haze and an emulsion in the presence of water.
2. Disclosure Statement
U.S. Pat. No. 4,747,851 discloses a novel polyoxy-alkylene diamine compound of the formula: ##STR2## where c has a value from about 5-150, b+d has a value from about 5-150, and a+e has a value from about 2-12. Motor fuel compositions comprising the novel polyoxyalkylene diamine, alone or in combination with a polymer/copolymer additive are also disclosed.
U.S. Pat. No. 4,659,337 discloses the use of the reaction product of maleic anhydride, a polyether polyamide containing oxyethylene and oxypropylene ether moleties, and a hydrocarbyl polyamine in a gasoline motor fuel to reduce engine ORI and provide carburetor detergency.
U.S. Pat. No. 4,659,336 discloses the use of the mixture of (i) the reaction product of maleic anhydride, a polyether polyamine containing oxyethylene and oxypropylene ether moieties and a hydrocarbyl polyamine, and (ii) a polyolefin polymer/copolymer as an additive in motor fuel compositions to reduce engine ORI.
U.S. Pat. No. 4,631,069 discloses an alcohol-containing motor fuel composition which additionally comprises an antiwear additive which is the reaction product of a dibasic acid anhydride, a polyoxyisopropylene diamine of the formula: ##STR3## where x has a value of 2-68, and an n-alkyl-alkylene diamine.
U.S. Pat. No. 4,643,738 discloses a motor fuel composition comprising a deposit-control additive which is the reaction product of a dibasic acid anhydride, a polyoxyisopropylene diamine of the formula: ##STR4## where x has a value of 2-50, and an n-alkyl-alkylene diamine.
U.S. Pat. No. 4,604,103 discloses a motor fuel deposit control additive for use in internal combustion engines which maintains cleanliness of the engine intake system without contributing to combustion chamber deposits or engine ORI. The additive disclosed is a hydrocarbyl polyoxyalkylene polyamine ethane of molecular weight range 300-2,500 having the formula: ##STR5## where R is a hydrocarbyl radical of from 1 to about 30 carbon atoms; R' is selected from methyl and ethyl; x is an integer from 5 to 30, and R" and R"' are independently selected from hydrogen and --(CH.sub.2 CH.sub.2 NH).sub.y --H, where y is an integer from 0 to 5.
U.S. Pat. No. 4,581,040 discloses the use of a reaction product as a deposit inhibitor additive in fuel compositions. The reaction product is the condensation product of the process comprising (i) reacting a dibasic acid anhydride with a polyoxyisopropylene diamine of the formula: ##STR6## where x is a numeral of about 2-50, thereby forming a bis-maleamic acid; (ii) reacting said maleamic acid with a polyalkylene polyamine, thereby forming a condensate product; and (iii) recovering said condensate product.
Motor fuel compositions which contain amine additives to control deposition include the following:
U.S. Pat. No. 4,357,148 discloses a motor fuel additive useful in controlling ORI which is the combination of (a) an oil-soluble aliphatic polyamine containing at least one olefinic polymer chain, and (b) a polymer, copolymer, or corresponding hydrogenated polymer or copolymer of a C.sub.2 -C.sub.6 mono-olefin with a molecular weight of 500-1,500.
An object of this invention is to provide a novel additive reaction product which may be employed as an ORI-reducing additive in a motor fuel composition.
Another object is to provide a fuel additive reaction product having a novel random backbone polyoxyalkylene radical in its structure.
Another object of this invention is to provide a fuel additive which exhibits a reduced sensitivity to tank water bottoms and which substantially reduces the formation of haze in a motor fuel and reduces the formation of an opaque emulsion.
Another object of this invention is to provide a motor fuel composition which is deposit-resistant and exhibits ORI-inhibition when employed in an internal combustion engine.
Yet another object of this invention is to provide a concentrate composition which may be added to a motor fuel to provide motor fuel compositions of the instant invention.